Integrated charging unit for passive refrigeration system

Abstract

A transport refrigeration system (TRS), a refrigerated transport unit, and a method of charging a thermal accumulator in a TRS are disclosed. The TRS includes a thermal accumulator including a phase change material (PCM) configured in a first state, to absorb thermal energy from the interior space of the transport unit during transformation to a second state. A heat exchanger, a portion of which is disposed within the thermal accumulator, is in thermal communication with the PCM. The TRS also includes an expansion device and a transport refrigeration unit (TRU). A heat transfer fluid circuit connects the TRU and the heat exchanger, and is configured to direct a heat transfer fluid from the TRU to the heat exchanger via the expansion device for charging the PCM.

What is claimed is: 
     
       1. A transport refrigeration system (TRS) for controlling refrigeration in an interior space of a transport unit, comprising:
 a thermal accumulator including a phase change material (PCM) configured in a first state, to absorb thermal energy from the interior space of the transport unit during transformation to a second state, wherein the PCM has a solid-liquid transition point in a range from −32° C. to 0° C. and the PCM is compatible with aluminum; 
 a heat exchanger, a portion of which is disposed within the thermal accumulator, wherein the portion is in thermal communication with the PCM, wherein the heat exchanger includes a plurality of passes disposed within the thermal accumulator; 
 an expansion device; 
 a transport refrigeration unit (TRU), the TRU including:
 a single compressor, and 
 a primary mover, the primary mover being mechanically coupled to the compressor to drive the compressor, wherein a speed of the compressor is proportional to 
 
 a speed of the primary mover; and 
 a heat transfer fluid circuit connecting the TRU and the heat exchanger, the heat transfer fluid circuit configured to direct a heat transfer fluid from the TRU to the heat exchanger via the expansion device for charging the PCM. 
 
     
     
       2. The TRS according to  claim 1 , wherein the TRU further includes a condenser. 
     
     
       3. The TRS according to  claim 1 , further comprising:
 a TRS controller configured to selectively enable and disable the TRU to meet a PCM temperature condition. 
 
     
     
       4. The TRS according to  claim 3 , wherein the TRS controller is configured to selectively enable the TRU when the PCM temperature condition is not met and selectively disable the TRU when the PCM temperature condition is met. 
     
     
       5. The TRS according to  claim 2 , wherein the PCM temperature condition includes one of an on-phase temperature range and a first state temperature. 
     
     
       6. The TRS according to  claim 3 , wherein the TRS controller is further configured to selectively enable the TRU when a shore power source is connected to the TRU. 
     
     
       7. The TRS according to  claim 1 , wherein the TRU is one of a high capacity TRU, a low capacity TRU, and a variable capacity TRU. 
     
     
       8. A method of charging a thermal accumulator in a transport refrigeration system (TRS) for a transport unit, the thermal accumulator including a phase change material (PCM) and a heat exchanger, and a heat transfer fluid circuit connecting a transport refrigeration unit (TRU) with the heat exchanger, wherein the PCM has a solid-liquid transition point in a range from −32° C. to 0° C., the PCM is compatible with aluminum, and the heat exchanger includes a plurality of passes disposed within the thermal accumulator, the method comprising:
 determining a PCM temperature based on a temperature corresponding to the PCM; 
 comparing the PCM temperature to a PCM temperature condition to obtain a comparison result; and 
 enabling the TRU based on the comparison result, wherein enabling the TRU includes:
 enabling a primary mover that is mechanically connected to a single compressor of the TRU such that the compressor is operated at a speed that is proportional to a speed of the primary mover. 
 
 
     
     
       9. The method according to  claim 8 , wherein determining the PCM temperature includes:
 determining a temperature of an interior space of the transport unit from a temperature sensor. 
 
     
     
       10. The method according to  claim 8 , wherein determining the PCM temperature includes:
 determining a temperature of the thermal accumulator. 
 
     
     
       11. The method according to  claim 8 , wherein the PCM temperature condition includes an on-phase temperature range and the enabling includes enabling the TRU when the temperature is outside the on-phase temperature range. 
     
     
       12. The method according to  claim 8 , further comprising:
 disabling the TRU when the PCM temperature condition is met. 
 
     
     
       13. A refrigerated transport unit, comprising:
 a transport unit including an interior space; 
 a transport refrigeration system, including:
 a thermal accumulator including a phase change material (PCM) configured in a first state, to absorb thermal energy from the interior space of the transport unit during transformation to a second state, wherein the PCM has a solid-liquid transition point in a range from −32° C. to 0° C. and the PCM is compatible with aluminum; 
 a heat exchanger, a portion of which is disposed within the thermal accumulator, wherein the portion is in thermal communication with the PCM, wherein the heat exchanger includes a plurality of passes disposed within the thermal accumulator; 
 an expansion device; 
 a transport refrigeration unit (TRU), the TRU including:
 a single compressor, and 
 a primary mover, the primary mover being mechanically coupled to the compressor to drive the compressor, wherein a speed of the compressor is proportional to a speed of the primary mover; and 
 
 a heat transfer fluid circuit connecting the TRU and the heat exchanger, the heat transfer fluid circuit configured to direct a heat transfer fluid from the TRU to the heat exchanger via the expansion device for charging the PCM. 
 
 
     
     
       14. The refrigerated transport unit according to  claim 13 , wherein the TRU further includes a condenser. 
     
     
       15. The refrigerated transport unit according to  claim 13 , further comprising:
 a TRS controller configured to selectively enable and disable the TRU to maintain a PCM temperature condition. 
 
     
     
       16. The refrigerated transport unit according to  claim 15 , wherein the TRS controller is configured to selectively enable the TRU when the PCM temperature condition is not met and selectively disable the TRU when the PCM temperature condition is met. 
     
     
       17. The refrigerated transport unit according to  claim 15 , wherein the PCM temperature condition includes one of an on-phase temperature range and a first state temperature. 
     
     
       18. The refrigerated transport unit according to  claim 15 , wherein the TRS controller is further configured to selectively enable the TRU when a shore power source is connected to the TRU. 
     
     
       19. The refrigerated transport unit according to  claim 13 , wherein the TRU is one of a high capacity TRU, a low capacity TRU, and a variable capacity TRU.